Why don't we close this ticket?
http://trac.sagemath.org/sage_trac/ticket/4566
There seems to be already a quite reasonable explanation to do this in
its comments
Maurizio
On 4 Set, 15:34, Burcin Erocal <bur...@erocal.org> wrote:
> Hi Jason and anybody interested in symbolics in Sage,
>
> On Fri, 04 Sep 2009 07:33:12 -0500
>
>
>
> Jason Grout <jason-s...@creativetrax.com> wrote:
>
> > Golam Mortuza Hossain wrote:
>
> > > On Sep 3, 10:52 am, Nicolas <nicolas.fresseng...@gmail.com> wrote:
> > >> I am trying to do the following thing but I am not sure whether
> > >> this is possible in sage (though I think it is in Mathematica)
>
> > >> Let's say I define a symbolic function
>
> > >> sage: f=function('f',x)
>
> > >> I would like to issue some command to "tell" sage what the
> > >> derivative of f is (for instance : g) so that the command
>
> > >> sage: diff(f)
>
> > >> would yield g
>
> > > Yes, its possible also in Sage. I am giving you an example that you
> > > can adapt for your need. (if you have have a function of multiple
> > > arguments then you should read diff_param keywords. For example,
> > > try heaviside?? in sage prompt to see how to read diff_param)
>
> > > --------
> > > sage: g = function('g')
> > > sage: def f_deriv(*args, **kwds):
> > > ....: return g(*args)
> > > ....:
> > > sage: f = function('f', derivative_func=f_deriv)
>
> > Where is this documented? I see some examples (of this and lots of
> > other keywords) under:
>
> > sage.symbolic.function.SFunction??
>
> > But I don't think most users would use sage_search or grep to find it
> > like I had to resort to after guessing a bunch of places the
> > documentation might be...
>
> > It looks like there are quite a lot of very interesting and useful
> > arguments to function. I had no idea these existed!
>
> This is some of the new functionality that came with the GiNaC wrapper.
> It was one of the first things I wrapped, and in the rush for the
> switch over from maxima, it still remains in its raw state.
>
> The interface to define new functions needs more care and polish. ATM,
> you define a class with methods _eval_, _evalf_, _derivative_, etc. and
> your function ends up being an instance of this class. I find this
> rather confusing and would appreciate any suggestions on other design
> options.
>
> There are still lots of rough edges in the new symbolics code. I don't
> have time to fix all these problems or write documentation. Though, I
> will do my best to answer questions and explain any tricky parts of the
> new symbolics to anybody interested, and put in the work to make the
> required changes (if any) at the c++ level in pynac.
>
> So if you're interested in getting the symbolics up to snuff, please
> take the plunge and look at the new symbolics code in sage/symbolic/.
>
> There are lot's of symbolics bugs on trac:
>
> http://is.gd/2SqFy[symbolics]http://is.gd/2SqMs[calculus]
>
> I can help fix the ones related to new symbolics, #6220 looks like a
> good start for example.
>
> If there is interest we can even hold a symbolics bug day where we meet
> on IRC and work on some of these.
>
> Cheers,
> Burcin
>
> P.S. Many thanks to Karl-Dieter and Golam for the patches waiting for
> review on trac. I'll try to do the reviews this weekend if no one gets
> there first.
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